Recording sheet for electrostatic photoprinting

ABSTRACT

A recording sheet for electrostatic photoprinting according to the present invention is provided with an insulating recording layer which is a resin formed on a conductive surface of an electrically conductive support, wherein said resin is a mixture of a resin soluble in organic solvents and also capable of swelling or soluble in water and a resin soluble in organic solvents but insoluble in water, the weight ratio of the former resin to the total weight of said mixture being in the range of 0.5 * 40 wt%.

Unlted States Patent [1 1 1111 ,840,399 Kobayashi 1 Oct. 8, 1974 1 RECORDING SHEET FOR 3,634,135 1/1972 Akiyama 117/221 E OS I PHOTOPRINTING 3,640,708 2/1972 Humphriss 3,674,474 7/1972 Kurokawa 96/15 [75] Inventor: Katsuomi Kobayashi, Tokyo, Japan [73] Assignee: Ricoh Co., Ltd, Tokyo, Japan Primary EXami'lerLe0n ROSdOl Assistant ExaminerMichael F. Esposito [22] Flled: July 1972 Attorney, Agent, or FirmCooper, Dunham, Clark, 21 Appl. No.2 274,976 Griffin & Moran I [30] Foreign Application Priority Data [57] ABSTRACT Aug. 3, 1971 Japan 46-57945 A recording Sheet for electrostatic Photopriming cording to the present invention is provided with an 521 US. 01 117/201, 117/218, 252/500 insulating recording layer which is a resin formed on a 51 1111.0 B44d l/18 Conductive Surface of an electrically conductive 9- [58] Field of Search 117/201, 218; 96/1.8; Port, wherein Said resin is a mixture of resin Soluble 52 5 in organic solvents and also capable of swelling or soluble in water and a resin soluble in organiesolvents 5 References Cited but insoluble in water, the weight ratio of the former UNITED STATES PATENTS resin to the total weight of said mixture being in the range of 0.5 40 wt%. 3,581,661 6/1971 Flecher 96/l.8 3,615,419 10/1971 Field 96/1.8 5 Claims, No Drawings RECORDING SHEET FOR ELECTROSTATIC PHOTOPRINTING BACKGROUND OF THE INVENTION a. Field of the Invention The present invention relates to a recording sheet for use in electrostatic photoprinting, which has an improved aptitude for writing thereon particularly with aqueous ink.

b. Description of the Prior Art Recording sheets for electrostatic photoprinting generally comprise a paper support in which one or both sides are electrically conductive with' recording resin layer formed on a side which is processed for electric conductivity. In order to record a desired image on suchan electrostatic recording sheet, the following methods are generally employed: (1) the electrostatic recording process, in which an original image is traced photoelectrically and the resulting electric signal corresponding to said image is introduced to a needle electrode, an electrostatic latent image corresponding to the original image is formed on the recording layer through electrification by discharging electricity from the electrode to the recording layer of the recording sheet according to said electric signal, and the thus formed latent image is developed with a dry or wet developer; and the (2) electrostatic latent image transferring process, wherein an electrostatic latent image is impressed on the photoconductive layer of an electrophotographic sensitive material by the conventional electrophotography, the thus formed latent image is transferred to the recording layer of the recording sheet, and then development is effected as described above.

The resins used to form the recording layer for these electrostatic recording sheets include such insulating resins as alkyd resin, epoxy resin, shellac, saturated polyester, polyethylene, vinyl acetate resin, vinyl chloride resin, vinyl acetate-vinyl chloride copolymer, styrene-butadiene copolymer, polymethyl methacrylate (US. Pat. No. 3,075,859), etc. However, recording layers including these resins are generally lacking in hydroscopicity and writability with a pencil or fountain pen because their surfaces are too smooth. To improve the writability with a pencil or fountain pen, it is known to mix inorganic pigments in the recording layers. The quantity of the inorganic pigment which is added to the recording layer for this purpose varies with writing instruments: to make it writable with a pencil, a small quantity will do, while to make it writable with a fountain pen using aqueous ink, a large quantity is required. However, a recording layer containing a large quantity of inorganic pigment is unsatisfactory because it has been found to discharge its surface electricity. No recording sheet is known which is suitable for writing with both a pencil and a fountain pen.

SUMMARY OF THE INVENTION The object ofthe present invention is to provide recording sheets for use in electrostatic photoprinting, which compensate for the aforementioned defects and, more particularly, improve writability in aqueous ink in particular without impairing the electrostatic properties of the recording layer of the sheets.

In other words, the present invention relates to re.- cording sheets for use in electrostatic photoprinting which are provided with insulating recording resin layers on the conductive surface of an electrically conductive support, wherein said resin is a mixture composed of a resin soluble in organic solvent and also capable of swelling or soluble in water and a resin soluble in organic solvent but insoluble in water, the weight ratio of the former resin to the total weight of said mixture being in the range of 0.5 40 wt%.

Said resin soluble in organic solvent and also capable of swelling or soluble in water (hereinafter referred to as the first resin) includes derivatives of cellulose such as hydroxypropylmethyl cellulose, ethyl hydroxyethyl cellulose, ethyl methyl cellulose, hydroxymethyl cellulose, homopolymers or copolymers formed from at least one member selected from the following group of A monomers, or copolymers formed from at least one member selected from the following group of A monomers and at least one member selected from the following group of B monomers: I

A ethylene glycol, diethylene glycol monomers:

propylene-glycol, vinyl methyl ether, maleic acid, maleic anhydride, ucr lic acid acryl amide, and vinyl pyrro idone B ethylene, styrene, vinyl acetate, acrylic monomers:

alkyl ester, and methacrylie alkyl ester (an alkyl radical having I 12 carbon atoms) Illustrative examples of resins consisting of A monomer above are as follows:

polyethylene glycol, polydiethylene glycol, polypropylene glycol,polyvinyl methyl ether, polymaleic acid, polymaleic anhydride, polyacrylic acid, po-

lyacryl amide, polyvinyl pyrrolidone, poly(vinyl methyl ether-maleic acid), poly(vinyl methyl ether-maleic anhydride), poly-(vinyl methyl ether-acrylic acid), poly(vinyl methyl ether-acryl amide), poly(vinyl methyl ether-vinyl pryrrolidone), poly(maleic acid-acrylic acid), poly(- maleic acid-acryl amide), poly(acrylic acid-vinyl pyrrolidone), poly(acryl amide-vinyl pyrrolidone), poly(ethylene glyeol-diethylene glycol), poly(ethylene glycol-propylene glycol), poly(vinyl methyl ether-maleic acid-acrylic acid),

poly(vinyl methyl ether-maleic acid-acryl am- -ethyl acrylate), poly(maleic acid-ethyl hexyl,

methacrylate), poly(maleic anhydride-ethylene), poly(maleic anhydride-styrene), poly(maleic anhydride-vinyl acetate), poly- (maleic anhydride-butyl acrylate), I

poly(acrylic acid-styrene), poly(acrylic acid-vinyl acetate), poly(acrylic acid-methyl methacrylate), poly-(acrylic acid-methyl acrylate), poly(acryl amide-styrene), poly(acryl amide-vinyl acetate), poly(acryl amide-ethyl acrylate), poly(acryl amide -butyl methacrylate), poly(vinyl pyrrolidone-styrene), poly(vinyl pyrrolidone -methyl acrylate), poly(vinyl pyrrolidone -ethyl methacrylate), poly(maleic acid-ethylene-styrene),

poly(vinyl methyl ether-styrene-methyl acrylate), poly-(vinyl methyl ether-ethyl acrylate-butyl methacrylate), poly(acrylic acid-acryl amide-styrene-butyl acrylate), ply(acryl amide-vinyl pyrrolidone-methyl acrylate-butyl methacrylate), etc.

The recording sheet according to the present invention is prepared by applying a solution obtained by dissolving any of the above exemplified resins together with a resin of the type which may be used in conventional electrostatic recording sheets which is soluble in organic solvents but is neither capable of swelling nor soluble in water, such as saturated polyester, polymethyl methacrylate, polyethyl methacrylate, polystyrene, polyvinyl butyral, epoxy resin, alkyd resin, polyethylene, polyvinyl chloride, styrene-butadiene copolymer, vinyl acetate-vinyl chloride copolymer, vinyl chloride-vinylidene chloride copolymer, in an appropriate organic solvent, or a dispersion obtained by adding at least one inorganic-pigment to said solution, if desired, onto the conductive surface of an electrically conductive support to the extent of about 2 20 g/m in dry weight to thereby ,form a recording layer thereon. The first resin, which is capable of swelling or soluble in water, to be employed for the present invention should also be soluble in organic solvents to ensure its uniform dispersion in the resulting recording layer. The percentage of the first resin to the total weight of resins contained in the recording layer should be in the range of 0.5 40 wt%. When the amount is less than 0.5 wt%, improvement of the writability cannot be expected, while in case it is more than 40 wt%, the hydroscopic property, or water absorbability, excessively increases with resulting deterioration of the electrostatic properties when the product is used at high humidity. The recording layer according to the present invention can contain inorganic pigments to the extent of 1 30 wt% based on the total weight of resins. In this way, not only writability with a pencil can be imparted but also writability in aqueous ink can be further improved. As the inorganic pigments for this purpose, barium titanate, titanium oxide, calcium sulfate, lithopone, silica, etc. having the grain size in the range of 0.001 p. are applicable.

As the support for use in the present invention, paper having its one side or both sides processed for electric conductivity, metal-laminated paper, metal foil and the like are applicable.

The following non-limiting examples illustrate the invention.

PREFERRED EMBODIMENTS OF THE INVENTION Example 1 By applying polyvinyl benzyl-quaternary ammonium chloride at the rate of 2 g/m onto one side of a slick paper consisting of 60 parts by weight of needle-leaved tree kraft pulp and 40 parts by weight of broad-leaved tree kraft pulp and weighing 55 g/m an electrically conductive paper support was prepared. Subsequently, by forming a recording layer through application of a solution having the following composition to the conductive surface of said support to a dry weight of 10 g/m an electrostatic recording sheet was prepared.

parts by weight methyl metaerylate-methyl acrylate copolymer (weight ratio=50:50) 60 polyvinyl methyl ether 40 benzene 250 butyl acetate parts by weight polyvinyl butyral methanol 300 toluene 100 and the solution- (2) having the following composition:

parts by weight hydroxy propyl methyl cellulose 20 methanol benzene to the conductive surface of the same electrically conductive paper support as that prepared by Example 1 to a dry weight of 7 g/r'n an electrostatic recording sheet was prepared.

Subsequently, after forming an electrostatic latent image on the photoconductive layer surface of an electrophotographic sensitive material through the conventional procedure, this latent image was transferred to the foregoing recording sheet and subjected to wet development followed by hot air drying. When the thus processed recording sheet was tested for ink fixability and writability by stamping with an aqueous stamp ink and writing in aqueous ink thereon, the results were excellent.

Example 3 I When an electric recording sheet was prepared in the same way as in Example 2 except for substituting ethyl hydroxy ethyl cellulose for hydroxy propyl methyl cellulose in the solution (2), and this recording sheet was tested. It proved excellent in writability in aqueous ink.

Example 4 When an electrostatic recording sheet was prepared in the same way 'asin Example 2 except for substituting ethyl methyl cellulose for hydroxy propyl methyl cellulose in the solution (2), and this recording sheet was tested on its properties, it proved excellent in writability in aqueous ink.

Example 5 When an electrostatic recording sheet was prepared in the same way as in Example 2 except for substituting parts by weight styrene-butadiene copolymer I (weight ratio=85:l5)

toluene benzene and the solution (4) having the following composition:

parts by weight polyethylene glycol 5 methylene dichloride to the conductive surface of the same electrically conductive paper support as that in Example 1 to a dry weight of g/m an electrostatic recording sheet was prepared. Subsequently, after forming an electrostatic latent image on the recording layer of this recording sheet through the conventional electrostatic recording procedure to be followed by dry development and heat fixing, test on the writability in aqueous ink was conducted. The results were excellent. Example 7 A dispersion was first prepared by adding 10 parts by weight of titanium oxide to a mixture of the solution (5) having the following composition:

tion:

vinyl methyl ether-mzileic 0.5 parts by weight anhydride copolymer (weight ratio=95:5) methyl ethyl ketone 10 parts by weight and then stirring thoroughly. By applying-this dispersion onto the conductive surface of the same electrically conductive paper support as that in Example 1 to a dry weight of 10 g/m an electrostatic recording sheet was prepared. Subsequently, the image was formed on this recording sheet in the same way as in Example 1. When tests were conducted on the writability in aqueous ink and in pencil, the results were quite excellent, and the fixability was also satisfactory. Example 8 By applying a solution having the following composition:

onto the conductive surface of the same electrically conductive paper support as that in Example 1 to a dry weight of 10 g/m an electrostatic recording sheet was prepared. Subsequently, after forming the image on this recording sheet in the same way as in Example 1, tests were conducted on the writability in aqueous ink and the fixability. The results were excellent. Example 9 An electrostatic recording sheet was prepared by applying a dispersion having the following composition:

parts by weight pulverized polyethylene I00 acrylic amide-methyl aerylute copolymer (weight rutio=5:-)5) methanol methyl ethyl ketone onto the conductive surface of the same electrically conductive paper support as that in Example 1 to a dry weight of 10 g/m an electrostatic recording sheet was prepared. Subsequently, after forming the image on this recording sheet in the same way as in Example I, a test was conducted on writability with aqueous ink. The result was excellent. Example 10 By applying a solution having the following composition:

onto the conductive surface of the same electrically conductive paper support as that in Example 1 to a dry weight of 10 g/m an electrostatic recording sheet was prepared. Subsequently, after forming the image on this recording sheet in the same way as in Example 1, a test was conducted on the writability with aqueous ink. The result was excellent. Example 11 A coating liquid was prepared by adding 30 parts by weight of silica to a solution having the following composition:

parts by weight and stirring with a homomixer for 30 minutes. By applying this coating liquid onto the conductive surface of the same electrically conductive paper support as that in Example 1 to a dry weight of 12 g/m an electrostatic recording sheet was prepared. When an electrostatic latent image was formed on the conductive layer of this recording sheet through the conventional electrostatic recording procedure followed by development with a liquid developer applicable to electrophotography and by natural drying, a satisfactory copied image was obtained. Further, the recording layer of this recording sheet proved writable with pencil as well as with aqueous ink, and the letters thus written did not disappeaer despite hard rubbing by hand.

Example 12 An electrostatic recording sheet was prepared in the same way as that in Example 1 1 except for substituting barium titanate for silica. The electrostatic properties and the writability of this electrostatic recording sheet were satisfactory.

Example 13 An electrostatic recording sheet was prepared in the same way as that in Example 1 1 except for substituting titanium oxide for silica. The electrostatic properties and the writability of this electrostatic recording sheet were satisfactory.

Example 14 An electrostatic recording sheet was prepared in the same way as that in Example 1 1 except for substituting calcium sulfate for silica. The electrostatic properties and the writability of this electrostatic recording sheet were satisfactory.

Example 15 An electrostatic recording sheet was prepared in the same way as that in Example 1 1 except for substituting lithopone for silica. The electrostatic properties and the writability of this electrostatic recording sheet were satisfactory.

What is claimed is:

1. A recording sheet for use in electrostatic photoprinting having an insulating recording resin layer formed on the conductive surface of an electrically conductive support, wherein said resin is a mixture compound composed of a first resin soluble in organic solvent and capable of swelling or soluble in water, and a second resin soluble in organic solvent but insoluble in water, the weight ratio of the first resin to the total weight of the mixture being from 0.5 -40 wt%; said first resin being selected from the group consisting of hydroxy propyl methyl cellulose, ethyl hydroxy ethyl cellulose, ethyl methyl cellulose, hydroxy methyl cellulose, polymers or copolymers consisting of at least one monomer selected from the A monomer group consisting of ethylene glycol, diethylene glycol, propylene glycol, vinyl methyl ether, maleic acid, maleic anhydride, acrylic acid, acryl amide and vinyl pyrrolidone, and copolymers consisting of at least one monomer selected from the A monomer group and at least one monomer selected from the B monomer group consisting of ethyl-- ene, styrene, vinyl acetate, acrylic alkyl ester, and methacrylic alkyl ester (an alkyl radical having l-l2 carbon atoms); and said second resin being selected from the group consisting of saturated polyester, polymethyl methacrylate, polyethyl methacrylate, polystyrene, polyvinyl butyral, epoxy resin, alkyd resin, polyethylene, polyvinyl chloride, styrene-butadiene copolymer, vinyl acetate-vinyl chloride copolymcr, and vinyl chloride-vinylidene chloride copolymer.

2. A recording sheet as defined in claim 1, wherein the recording layer further contains inorganic pigment to the extent of 1 30 wt% based on the total weight of said mixture.

3. A recording sheet as defined in claim 2, wherein said inorganic pigment is selected from the group consisting of barium titanate, titanium oxide, calcium sulfate, lithopone and silica having a grain size in the range of 0.001 10,u., respectively.

4. A recording sheet as defined in claim 3, wherein said mixture of the former resin and the latter resin consists of polystyrene and ethylene glycol.

5. A recording sheet as defined in claim I wherein said mixture is selected from the group consisting of the following mixtures: 

1. A RECORDING SHEET FOR USE IN ELECTROSTATIC PHOTOPRINTING HAVING AN INSULATING RECORDING RESIN LAYER FORMED ON THE CONDUCTIVE SURFACE OF AN ELECTRICALLY CONDUCTIVE SUPPORT, WHEREIN SAID RESIN IS A MIXTURE COMPOUND COMPOSED OF A FIRST RESIN SOLUBLE IN ORGANIC SOLVENT AND CAPABLE OF SWELLING OR SOLUBLE IN WATER, AND A SECOND RESIN SOLUBLE IN ORGANIC SOLVENT BUT INSOLUBLE IN WATER, THE WEIGHT RATIO OF THE FIRST RESIN TO THE TOTAL WEIGHT OF THE MIXTURE BEING FROM 0.5-40 WT%; SAID FIRST RESIN BEING SELECTED FROM THE GROUP CONSISTING OF HYDROXY PROPYL METHYL CELLULOSE, ETHYL HYDROXYL ETHYL CELLULOSE, ETHYL METHYL CELLULOSE, HYDROXY METHYL CELLULOSE, POLYMERS OR COPOLYMERS CONSISTING OF AT LEAST ONE MONOMER SELECTED FROM THE A MONOMER GROUP CONSISTING OF ETHYLENE GLYCOL, DIETHYLENE GLYCOL, PROPYLENE GLYCOL, VINYL METHYL ETHER, MALEIC ACID, MALEIC ANHYDRIDE, ACRYLIC ACID, ACRYL AMIDE AND VINYL PYRROLIDONE, AND COPOLYMERS CONSISTING OF AT LEAST ONE MONOMER SELECTED FROM THE A MONOMER GROUP AND AT LEAST ONE MONOMER SELECTED FROM THE B MONOMER GROUP CONSISTING OF ETHYLENE, STYRENE, VINYL ACETATE, ACRYLIC ALKYL ESTER, AND METHACRYLIC ALKYL ESTER (AN ALKYL RADICAL HAVING 1-12 CARBON ATOMS); AND SAID SECOND RESIN BEING SELECTED FROM THE GROUP CONSISTING OF SATURATED POLYESTER, POLYMETHYL METHACRYLATE, POLYETHYL METHACRYLATE, POLYSTYRENE, POLYVINYL BUTYRAL, EPOXY RESIN, ALKYD RESIN, POLYETHYLENE, POLYVINYL CHLORIDE, STYRENE-BUTADIENE COPOLYMER, VINYL ACETATE-VINYL CHLORIDE, COPOLYMER, AND VINYL CHLORIDE-VINYLIDENE CHLORIDE COPOLYMER.
 2. A recording sheet as defined in claim 1, wherein the recording layer further contains inorganic pigment to the extent of 1 * 30 wt% based on the total weight of said mixture.
 3. A recording sheet as defined in claim 2, wherein said inorganic pigment is selected from the group consisting of barium titanate, titanium oxide, calcium sulfate, lithopone and silica having a grain size in the range of 0.001 * 10 Mu , respectively.
 4. A recording sheet as defined in claim 3, wherein said mixture of the former resin and the latter resin consists of polystyrene and ethylene glycol.
 5. A recording sheet as defined in claim 1 wherein said mixture is selected from the group consisting of the following mixtures: 